Pot type furnace for molten metal



Nov. 16, 1954 POT TYP Filed Feb. 2, 1955 K. A. LANG E FURNACEFOR MOLTEN METAL 2 Sheets-Sheet l 46m Mfmm ATTURNEYS.

United States Patent U M PQTtTY PE EURNACE FORMQLTENME'IAL v Karl.. A. Lang,y Glenview, 111;assignory to Lindberg-.En-

gineering Company,I Chicago, ,Ill.', ka corporationY of Illinois.

AlrxplicationA February 2, 1953, Serial No. 334,465 9 Claims.. (CL 13---22)\A This. invention .relatesv to pot type furnaces for'v molten metaLand more particularlytot electric resistance furnacesy for melting or holdingmolten metal.

It is one yof .theobjects ofthe .invention to provide a pot .type furnace in which the heatingelement is very simplein.l construction, is easily mounted inthe furnaceandprovides uniform heatingfor the metal in the furnace.

According to one important .feature .ofthe-invention, the;,heating element is tubular and is mounted around thegmetalholding cavityin the furnacevbody with terminals connected totheelement and extending. through the .walls of the furnace body for connection to a sourcey of` heating. current.,

Another object is to.provide a pottype furnace in which.the heating element. is completely embedded in the .refractory furnace body around the metal receiving cavity in thebody so that only refractory is exposed at the inner surface of they cavity to receive-a metal such as aluminum.

In anralternative arrangement for metals, such as magnesium, the: heating element lines the cavity and means .are provided in the furnace bodyl to hold a separate pot or Crucible in the cavity spaced from the heating element.

A'further object lis to provide a pot type furnace in which the. heating elementv can easily be arranged to accommodate any` desired. type` of operating. current, such as single phase, double phase. or 'three phase.

The above and other objects and featuresofthe invention will 4be more readilyI apparenti from the following descriptionf yWhen ,ready in connection with the accompanying drawing in which:

Figure'l is a top plan view of a furnace embodying the-f invention;

Figure 2 is a section onthe line 2-- 2 of Figure l;

Figure 3. is a perspectiveviewof theheating element;

Figure 4 is asectionsimilar to Figure 2 of a modified form of furnace,.and.A

Figures 5, 6 and 7 are perspective views of modified forms of heating elements.

The furnace, as shown in Figures l to 3, is primarily designed to melt aluminum or to hold aluminum in molten condition. As shown, the furnace comprises a body 10 formed of a refractory material and having a central cylindrical cavity 11 therein to receive the metal. It will be understood that the pot might be enclosed by a metal housing and supported in any desired manner at a convenient height.

Metal within the cavity 11 is adapted to be heated by an electrical resistance element 12 which is tubular in form and which may be formed of any desired resistance material such as a nickel chrome alloy. The tubular heating element 12 is of larger diameter than the cavity 11 and is completely embedded in the body concentric with the cavity body. In a preferred construction, there may be from one to one and a half inches of refractory material on the inside of the heating element dening the walls of the cavity. With this construction, the metal in the cavity contacts only the refractory material which is highly desirable in the case of metals like aluminum which would react with the heating element.

Heating current is supplied to the heating element 12 through terminals 13 and 14, which, as shown in the form of conducting bars, extend through the walls of the refractory body 10 at diametrically opposite points. The inner ends of the terminals may be bent over as shown 2,694,740 Ptented ZNov. 16 1954,

ICC

tol-increase thel area of contactwithgthea heating element 12. and-may be: lintimately. securedit'oitheA heating Y element as by welding. Theaouterendsof: the terminals :project beyond the.VV body; for. connection tog a sourceoff heatingy current. In the constructiontshownf.in'iFiguresl to` 3, it is intended that the heating current-employed: be single .phase current..

1n use, it will .beaseentthat/becausether-heating. element is completelytembeddedifin.vthecrefractoiy body,` the. metal cannot contact.-th'e-.heating.element-at anyl time. The heating elementlcanx easily.. beimounted in the ypot. during pouringcof. the.refractory..-material and` the terminals. will bei.secureiyfembeddedx-inthe, pot at4 the' samey time. Whenvcurrentuis supplied the: .heating element will heat uniformly' completelyaroundthe cavity 11 so that metal-therein-will be uniformly heated and diiculties due. to' unevenA expansionor contraction ofthe material-will be. avoided;

Fory melting` metals, such as 1 magnesium, which' would react with therefractory, the construction maybe modiiied as shown in Figure 4. In: thisconstruction, the furnace comprisesa pot 15foffrefractory material formed with a central cylindrical cavity` and having1 a tubular heating elementl liningnthe.wallsMof-the cavity with its topsand .bottom terminatingl short4 ofuthe Aends-of thecavity. The: element..16:may.be1 identical with the element. 12 with the. difference thatthe'I relative diametersof .the element andtheicavityl are altered so that the element will be exposed at -theinnensurface of thecavity, as shown. Terminals 17fandl183are connected toy diametrically oppositexpoints .oncthe element andextend. through. the; .walls of thes body 'forx connection to a current source.

The molten metal is adaptedtobe held-in a separato pot or crucible 19 whichformetalssuchfas magnesium' might be formed .of-iron' or.l steel. The'- pot 19- is of smaller diameter: than .thenelement-land is held in spaced relation thereto by a top iiange- 21 fitting into an annular recess in the` top.` of thet furnace `cody. ln addition, vif desired, .the .bottom-.of the cavity in the furnace body may be deiinedbya reduced-diameter annular shoulder 22-to .engagethen sides -of Ithe pot.

In this construction, the metal is contained entirely within the pot..19 which. is.hel d.-rinfspaced relation to the heatingfelement1and`whichv is heated by radiation and. conductionfrom the; heating element Otherwise, the operation is identical'. with thatof.-Figuresl to 3.

Figure 5 illustrateswan alternative form of-heatingelement for use with'two phase vcurrent.-VY As shown, a tubular heatingI element 23V is providedewhichvis axially split, as indicatedaat 24. ThreeterminalsZS, -26 and 27 are employed.. Theterminal -25 is secured. to the heating element vat av pointdiametricallyfopposite to the split 24 and the terminals 26 and 27 are connected to the element closely adjacent to and on opposite sides of the split 24.

This element may be mounted in a furnace body in exactly the same manner as the element 12 of Figures l to 3 or the element 16 of Figure 4. In use the terminals are connected to the leads of a two phase three wire source with the terminal 25 being connected to the center lead and the terminals 26 and 27 connected to the outside leads. As shown for current balance the terminal 25 may be split and folded in opposite directions from its center over the resistance element.

Figure 6 illustrates another variation of heating element for use with single phase current. This element comprises a tubular resistance 28 split along one side as indicated at 29. A pair of terminals 31 and 32 extend parallel to the axis of the tubular element 28 and are secured thereto on opposite sides of the split 29 by welding or the like.

The element 28 can be mounted in a furnace body, as shown in either Figures 1 to 3, or in Figure 4, and when so mounted, the terminals 31 and 32 will extend out through one end, either the bottom or the top wall of the body, for connection to a current source.

Figure 7 shows an element adapted for three phase current and comprises a tubular resistance 33 having three terminals 34, 35 and 36 secured thereto at uniformly spaced points in its periphery. This element is mounted in a furnace body in the 'same ways as the element discussed above with the single difference that the three terminals are connected tothe three wires of a three phase current source.

While several embodiments of the invention have been shown and described in detail, it will befunderstood that these are illustrative only and are not to be taken as a definition of the scope of the invention, reference being had to the appended claims.

What is claimed is:

1. A pot type furnace for molten metal comprising a cup shaped body of refractory material formed with a central cavity therein having an open top and an integral closed bottom, a substantially tubular resistance element in the body around the cavity therein, the resistance element being open at the top and bottom and being substantially coextensive axially with the cavity and terminals secured to and extending outward from the resistance element through the walls of the body for connection to a source of electric current.

2. A pot type furnace for molten metal comprising a cup shaped body of refractory material formed with a central cavity therein having an open top and an integral closed bottom, a substantially tubular resistance element in the body around the cavity therein, the resistance element being open at the top and bottom and being substantially coextensive axially with the cavity and terminals secured to and extending outward from the resistance element through the walls of the body for connection to a source of electric current, the resistance element being completely embedded in the walls of the body so that only refractory material is exposed at the inner surface of the cavity.

3. A pot type furnace for molten metal comprising a cup shaped body of refractory material formed with a central cavity therein, a substantially tubular resistance element in the body around the cavity therein, and terminals secured to and extending outward from the resistance element through the Walls of the body for connection to a source of electric current, the resistance element fitting against the inner surface of the cavity and being exposed at the inner surface of the cavity, a pot to hold metal of smaller external diameter than the internal diameter of the resistance element, and intertting parts on the body and the pot to hold the pot centered in the cavity in spaced relation to the resistance element.

4. A pot type furnace for molten metal comprising a cup shaped body of refractory material having a central cavity therein having an open top and an integral closed bottom, a tubular resistance element in the body around the cavity, the resistance element being open at the top and bottom and being substantially coextensive axially with the cavity and a plurality of terminals secured to the resistance element at uniformly spaced points around its circumference and extending therefrom through the body for connection to a source of electric current.

5. A pot type furnace for molten metal comprising a cup shaped body of refractory material having a central cavity therein, a tubular resistance element in the body around the cavity, and three terminals secured to the resistance element at three evenly spaced points around the circumference of the resistance element and extending therefrom through the walls of the body for connection to a source of three phase current.

6. A pot type furnace for molten metal comprising a cup shaped body of refractory material having a central cavity therein, a tubular resistance element in the body around the cavity, said resistance element being split axially at one point in its circumference, and terminals connected to the resistance element at opposite sides of the split and extending through the body for connection to a source of electric current.

7. A pot type furnace for molten metal comprising a cup shaped body of refractory material having a central cavity therein, a tubular resistance element in the body around the cavity, said resistance element being split axially at one point in its circumference, and three terminals connected to the resistance element and extending therefrom through the walls of the body for connection to a source of two phase electric current, one of the terminals being connected to the body diametrically opposite to the split and the other two closely adacent to and on opposite sides of the split.

8. A pot type furnace for molten metal comprising an integral unitary body of refractory material having a cup shaped cavity formed in the top thereof, a thin walled tubular metal heating element open at its top and bottom mounted in the body around the cavity and substantially coextensive axially with the cavity, and a plurality of terminal bars extending through the body into contact with the thin walls of the heating element and having end portions overlying and secured to the walls of the heating element throughout a substantial area.

9. A pot type furnace for molten metal comprising an integral unitary body of refractory material having a cup shaped cavity formed in the top thereof, a thin walled tubular metal heating element open at its top and bottom mounted in the body around the cavity and substantially coextensive axially with the cavity, and a plurality of terminal bars extending radially inward through the body to the heating element and having turned over ends fitting against and secured to the walls of the heating element over a substantial area.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 769,250 Conley Sept. 6, 1904 1,023,309 Helberger Apr. 16, 1912 1,023,996 Conley Apr. 25, 1912 1,100,972 Hampton June 23, 1914 1,335,079 Speirs Mar. 30, 1920 

